Attachment for drawing compasses



Jan. 9, 1951 w. F. qAmlsoN ET AL 2,537,058

ATTACHMENT "TFOR DRAWING COMPASSES Filed March 19, 1945 I N V EN TORS 9042453424) E?) jawioow, ficvr/ea/a fie). five/w $444444 Patented Jan. 9, 1951 ATTACHMENT FOR DRAWING GOMPASSES Winfield F. Jamison and Charles W. Van Buren, Brunswick, Ga.

Application March 19, 1945, Serial No. 583,452

4 Claims.

Our invention relates broadly to geometric instruments and more particularly to an improved construction of geometric instrument requiring the swiveling of a graphic member about a center point and the selection and maintenance of the center in a predetermined position.

One of the objects or" our invention is to provide an improved construction of geometrical instrument in which improved means are provided for fixing and maintaining the center element about which the instrument may be rotated for scribing curved lines or measuring distances between certain centers.

Another object of our invention is to provide an attachment for geometrical instruments such as dividers, compasses, scribers, beam-trammels, and the like for facilitating the setting of the center element and maintaining the center element in a set.

A further object of our invention is to provide an improved construction of attachment for geometrical instruments having means for fixing the center element of the instrument and preventing skidding thereof while permitting adequate visibility for setting the center element of the geometrical instrument upon a predetermined center point.

Still another object of our invention is to provide a construction of attachment for geometricalinstruments formed from yieldable material having transparent Wall portions set therein for permitting a suction grip to be established between the geometrical instrument and a plane surface while enabling adequate visibility through the walls of the suction device for setting the geometrical instrument upon a predetermined center point in the plane surface.

A still further object of our invention is to provide a construction of attachment for geometrical instruments formed from plastic material of composite character including a portion attachable to the center element of the geometrical instrument, a substantially transparent cup-like portion and a peripheral and yieldable gripping portion secured to the cup-like portion for enabling a suction grip to be established between a plane surface and the center element of the geometrical instrument with adequate visibility for applying the center element of the geometrical instrument upon a predetermined center point in the plane surface. 7

Gther and further objects of our invention will be understood from the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a schematic view showing the application of the attachment of our invention to a geometrical instrument of the compass variety and illustrating the attachmentin vertical 580* 239 and hqw nsih m n i wh h'm center point to which the compass is applied may be visually observed through the attachment device; Fig. 2 is a side elevational view of the attachment device of our invention; Fig. 3 is a transverse section taken through the device of our invention on line 3-3 of Fig. 2; Fig. 4 is a side elevational View of a modified form of attachment device embodying our invention in which full visibility of the center point to which the geometrical instrument may be applied is permitted; Fig. 5 is a transverse sectional view taken on line 5-5 of Fig. 4; Fig. 6 is a vertical sectional view through the structure illustrated in Figs. 4 and 5 taken on line 5-5 of Fig. 5; Fig. '7 is a side elevational view of a further modified form of our invention in which plastic windows or viewing apertures are provided in the side walls of the attachment device to permit visibility in the setting of the center of the geometrical instrument upon an inscribed center point on a plane surface; Fig. 8 is a transverse sectional view through the attachment device of Fig. 7 taken on line 8-8 thereof; Fig. 9 is a vertical sectional View through the attachment of Figs. 7 and 8 takenon line Q-S of Fig. 8; and Fig. 10 is a transverse sectional view taken on line m m of Fig.1 and illustrating the construction of swivel used in the geometrical instrument of our invention.

Our invention is directed to a simple and inexpensive attachment for geometrical instruments whereby the center element of theigeometrical instrument is rendered non-skid and may be readily centered onto an inscribed center point on a plane surface for drawing circles about the inscribed center point and restored to the center point with suificient adhesion to the plane surface to prevent normal accidental displacement from the plane surface. The cup-like device is provided with a sighting aperture or apertures to allow adequate vision with respect to the center point to which the geometrical instrument is to be applied. The cup-like device has a hub portion carrying an insert which is screwthreaded to allow a set screw to be adjustably extended therethrough for engaging the geometri cal instrument. The cup portion is extended a provide a relatively adhesive peripheral surface forming anti-skid means with respect to theplane surface against which the geometrical instrument is applied.

In another form of our invention the attachment is molded from plastic materials in which the hub portion of the device is substantially rigid and forms a supporting means for an adjusting screw by which the attachment is applied to the geometrical instrument. The substan-. tially rigid portion of the attachment is united with a plastic substantially transparent portion extending into a cup-like configuration the periphery of which is provided with a yieldable;

engaging surface. The yieldable engaging surface enables the attachment to be secured to a plane surface in the nature of a suction or vacuum 'cup for maintaining the geometrical instrument on an inscribed center point. The transparent portion of the attachment enables the inscribed center point to be clearly viewed in setting the device on center point or in restoring the device to the inscribed center point from time to time.

In still another form of our invention we provide a yieldable rubber-like suction or vacuum cup as an attachment for geometrical instruments and wherein the side walls of the suction or vacuum cup have molded transparent inserts therein which provide adequate visibility for the inscribed center point on a plane surface to which the geometrical instrument is to be applied. The transparent inserts maintain the vacuum within the attachment while permitting adequate visibility through the walls of the cup. In the several forms of our invention we provide a construction of swivel joint in the geometrical instrument whereby the center when once set may be maintained in said position while permitting rotation of the scriber portion of the geometrical instrument around the center point.

Referring to the drawings in more detail reference character I designates a plane surface against which the geometrical instrument of our invention is arranged to operate. The geometrical instrument includes a center element which we have shown generally at 2 which terminates in a point 3 which may be set on an inscribed center point on plane surface I. The center element 2 is connected through a swivel joint 4 with arm 5 which connects through pivoted joint 6 with the arm I of the geometrical instrument. Arm I terminates in a pivoted joint 8 to which is also connected the arm 9. An arm III is connected through pivoted joint II with arm 9 and serves as a support for the scriber which we have represented generally at I2. A finger grip I4 is provided extending from pivoted joint 8 for enabling the scriber I2 to be revolved about center element 2. In inscribing circles on plane surface I with the center element 2 set on the inscribed center point by engagement of point 3 therewith, the geometrical instrument may be rotated with the rounded surface la of swivel joint 4 coacting with rounded surface 4b of swivel joint d. The

rounded surfaces 4a and 4b are provided on the' adjacent extremities of center element 2 and arm 5 respectively as shown. These rounded surfaces 4a and lb substantially reduce frictional forces at the swivel joint and facilitate the use of the instrument for the inscribing of relatively large circular figures. Center element 2 and arm 5 are diametrically apertured as represented at 2a and 5a respectively which allows the introduction of a headed rivet member I5 through the apertured surface of the rounded end of one of the coacting aligned members 2-5 and the upsetting of the end of the rivet to form a head thereon for securing the rivet with respect to the apertured coacting rounded end of the other of said members 2-5.

For the purpose of securing the center element 2 against skidding with respect to plane surface I we provide the attachment shown in Figs. 1, 2 and 3. The attachment comprises a flexible rubber-like cup I6 having a hub portion IT with an internal diameter substantially conforming with the external diameter of the center element 2. The hub portion I! has a metallic bushing I8 sented at 30, 3i and 32.

molded through one side thereof. The metallic bushing I8 is internally screw-threaded to receive the adjustment screw I9. Adjustment screw I9 has a knurled head 20 thereon by which the adjustment screw may be moved under control of the fingers against the center element 2 for detachably connecting the attachment of the center element 2. The yieldable rubber-like cup I6 has a multiplicity of sighting apertures 2I therein each disposed on axes extending in a radial and angular direction with the inscribed center point on plane surface I as pivot point. It is therefore readily possible to visually sight through apertures 2| to set thepoint 3 of center element 2 precisely on the inscribed center point of plane surface I which might otherwise be obscured by the rubber-like cup I6. Thev annular peripheral edge 22 of rubber-like cup I5 engages the plane surface I in an annular path about the inscribed center point on plane surface I and prevents accidental dislodgment of the point 3 from the inscribed center point under all normal conditions of use.

In the form of our invention shown in Figs. 4, 5 and 6 the attachment is molded from materials of three different characteristics. The hub portion of the attachment illustrated at 23 is formed from substantially rigid plastic material and serves to support internally screw-threaded bushing I8 through which adjustment screw I9 extends. The substantially rigid plastic material 23 is united end to end with the cylindrical portion 24 of the transparent cup-like member 25. The transparent cup-like member 25 is formed from transparent plastic through which the inscribed center point on plane surface I may be readily viewed in setting the geometrical instrument initially and in restoring the geometrical instrument to the inscribed center point from time to time. The transparent cup-like member 25 terminates in a yieldable peripheral portion 25 which is engageable with the plane surface I in such manner that the cup-like member 25 is effective as a suction or vacuum cup. As the yieldable peripheral edge portion 26 is forced toward the plane surface I air is partially excluded from the cup-like member 25 so that when the resilient edge portion 26 tends to restore to its original position by springing cup-like member 25 away from plane surface I a vacuum is established within cup-like member 25 so that atmospheric pressure tends to maintain the attachment in position thus maintaining the center element 2 in set position.

In the form of our invention illustrated in Figs. '7, 8 and 9 the attachment is formed from soft rubber of the general construction illustrated in Fig. 1 and includes a resilient hub portion I'I carrying internally screw-threaded bushing I8 for receiving adjustment screw I9 controlled by knurled thumb screw 25. The resilient cup-like portion I5 is provided with apertures in the walls thereof as presented at 2'1, 23 and 29. The apertures 2T, 28 and 29 are disposed on axes which extend substantially radial to an apex at the inscribed center point on the plane surface I. In

each of these apertures 21, 28 and 29 we provide transparent inserts of plastic material repre- The plastic inserts are each shaped to provide a somewhat spherical curvature to conformwith the contour of the cup-like portion I6 of the attachment. Each plastic insert is provided with a peripheral tongue-like projection as represented at 32a in Fig. 9. The peripheral tongue-like projection on each transparent plastic insert 30, 3I and 32 tends to imbed itself in the yieldable material of the attachment for maintaining the plastic in-- serts in position regardless of the fact that the cup-like portion I6 of the attachment may become somewhat deformed as the attachment is applied to the plane surface I. The cup-like portion I6 of the attachment terminates in an enlarged peripheral edge portion represented at 33 arranged to engage the plane surface I for establishing a relatively air-tight seal therewith so that as air is excluded from the interior of the cup-like portion I6 upon applying the attachment to the plane surface I, the tendency of the cup-like portion IS in springing outwardly to a restored position from the deformed position thereof tends to create a vacuum introducing sufiicient suction to maintain the center element 2 with respect to the plane surface I.

In the forms of our invention shown in Figs. 4-9 the sighting aperture or apertures are connected with the hub portion and the cup-like portion in a substantially vacuum tight manner so that a vacuum may be maintained between the cup-like portion and the plane surface.

In the forms of our invention illustrated in Figs. 4-9 the vacuum when once established between the attachment and plane surface I may be broken for removing the geometrical instrument from plane surface I by forcefully lifting the instrument from the plane surface I or passing a, sharp blade beneath the peripheral edge of the attachment and the plane surface for equalizing the external and internal pressures with respect to the attachment, thereby enabling the geometrical instrument to be readily removed from the plane surface ready for replacement at any time.

Our invention is particularly applicable for use in the glazing industry where it is often desirable to operate a scriber on a smooth plate of glass. The anti-skid attachment of Figs. 1-3 or the vacuum attachments of Figs. 49 greatly facilitate precision and rapid work on surfaces of such smooth characteristics. Our invention is also a substantial time saver in aeronautical, architectural and marine drafting where curves must be drawn expeditiously and where compasses must be applied at frequent intervals to prescribed centers.

A wide variety of plastics may be employed for the manufacture of the device of our invention and we intend no restrictions as to the kinds of materials which may be employed.

While we have described our invention in certain of its preferred embodiments we realize that changes in detail may be made and we intend no limitations upon our invention other than may be imposed by the scope of the appended claims.

What we claim and desire to secure by Letters Patent of the United States is as follows:

1. An attachment for geometrical instruments of the type including a center element engageable with a plane surface, comprising a composite member including av cylindrical portion, a cuplike portion and a yieldable peripheral portion united end to end forming a vacuum tight closure engageable with said plane surface in a substantially vacuum tight manner, said center element passing through said cylinder portion and projecting into said cup-like portion, said yieldable peripheral portion having an annular edge engageable with the plane surface with which said center element coacts and said cup-like portion being optically transparent for facilitat ing the setting of the center element on an inscribed center point of said plane surface and means for detachably securing said cylindrical portion to said center element.

2. An attachment for geometrical instruments of the type including a center element engageable with an inscribed center point on a plane surface, comprising a body structure including a cylindrical portion and a cup-like portion, means extending through said cylindrical portion and detachably engageable with the center element, said center element extending through said cylindrical portion and projecting into said cup-like portion, means carried by the periphery of said cup-like portion for engaging the plane surface in an annular zone about said center element forming a vacuum tight closure with said plane surface and an optically transparent portion in the side wall of said cup-like portion for visually observing the position of the said center element with respect to an inscribed center point on the plane surface.

3. An attachment for geometrical instruments of the type including a center element engageable with a plane surface, comprising a composite member including a cylindrical portion, a combination cylindrical and cup-like portion of optically transparent material, with the said last mentioned cylindrical portion connected with said first mentioned cylindrical portion in a substantially vacuum tight manner and a yieldable peripheral portion connected with the peripheral edge of said cup-like portion in a substantially vacuum tight manner, said center element passing through said two cylindrical portions and extending into the cup-like portion, said yieldable peripheral portion having an annular enlarged fiat edge engageable with the plane surface with which said center element coacts whereby said center element may be set upon a center point on said plane surface where the center point is unobstructedly visible through said optically transparent combination cylindrical and cuplike portion of said composite member.

4. An attachment for geometrical instruments of the type having a center element engageable with a plane surface comprising in combination with the center element of the geometrical instrument a plastic member comprising a substantially rigid hub-like portion and a cup-like portion connected therewith, said hub-like portion having a substantially vacuum-tight detachable connection with respect to the center element, said cup-like portion being optically transparent and having a substantially vacuum-tight connection with said hub-like portion and a yieldable peripheral edge portion having a substantially vacuum-tight connection with said optically transparent cup-like portion, said edge portion terminating in an annular face for engaging the plane surface in an annular zone about the center element.

WINFIELD F. JAMISON. CHARLES W. VAN BUREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 288,235 Hanstein Nov. 13, 1883 951,255 McMurray Mar. 8, 1910 985,968 Beck Mar. '7, 1911 1,263,182 Wolthausen Apr. 16, 1918 

